Kinetics of Methane Clathrate Hydrate Formation in Water-in-Oil Emulsion

Abstract

The methane hydrate formation kinetics in water-in-oil (w/o) emulsion was measured using the pressure–volume–temperature (PVT) method during isochoric, isothermal processes at an initial pressure of 6.80 MPa in an agitated reactor. The effects of agitation rates (n) of 300–1100 rpm, average water droplet diameters (d̅) at 30% water cut, and temperatures (T) of 269.15–277.15 K on the induction time and hydrate formation rate were systematically studied. The experimental results show that the induction time of hydrate formation initially decreased as the agitation rate increased and then increased when higher agitation rates were used. The results did not reveal any influence of the average diameter of the water droplets on induction time. Increasing the temperature increased the induction time. The rate of hydrate formation increased as the agitation rate increased and the average diameter and temperature decreased. The total methane hydrate formation was affected by the average diameter and temperature, and the hydrate formation rate was enhanced in w/o compared with many other methods. A mathematical model of hydrate formation kinetics in w/o was established based on crystal growth theory and the mass transfer of methane. The effects of the amounts of hydrate in a w/o system on the mass-transfer coefficient of the oil/water interface were considered by introducing an empirical equation. The parameters of the model were determined by correlating the experimental data with the model data. The agreement between the experimental data and the calculated results of the model was satisfactory.